Crawler tractor track chain drive assemblies are commonly used in industry, and they include links which are pinned together and which have track plates for engaging the ground and with the track chain being engaged by sprocket teeth for driving the track chain in advancing the tractor over the ground. One isolated example of that general type of prior art is found in U.S. Pat. No. 3,588,195 wherein the sprocket directly engages bushings surrounding the pins which hold the links together. In that prior art, the problem is related to the fact that the sprocket directly contacts the chain bushings, and this causes wear and unnecessary noise and the life and actual efficiency of the assembly is not as great as that possible with the present invention.
Other prior art examples of track chain assemblies are found in U.S. Pat. Nos. 3,563,614 and 3,567,294 and 3,680,929. In those three patents, there are teachings of arranging a track chain with a midpoint driving lug which is engaged by the sprocket for advancing the tractor over the ground. However, in those prior art arrangements, the driving lugs shown therein are of a rigid material and they all require positioning and bolting in the track chain. Also, U.S. Pat. Nos. 1,638,140 and 3,854,345 show track chain assemblies which have resilient pieces included therein, though the resilient pieces are shown mounted on the sprocket of the assembly, and the showings are not of an assembly which has a so-called midpitch or point drive which utilizes the lug on the track chain.
The present invention provides an improvement over the crawler tractor track chain drive assemblies heretofore known, and, more particularly, it provides a drive arrangement of the type having the center or midpitch drive bushing on the track chain and having the advantages of an efficient drive relation between the chain and the sprocket, in that a large number of the sprocket teeth can engage the chain in full drive at all times, and shock loads are reduced and there is less noise, all of which is achieved by an assembly made according to this invention.
The present invention specifically provides a crawler tractor track chain drive assembly which utilizes the center-mounted drive bushing on the track chain but which does not require that the bushing be bolted, screwed, or otherwise fastened to the chain, and, further, the bushing of this invention is of an elastomeric material which permits the bushing to adapt and adjust to both the track chain and to the teeth of the engaging sprocket, all for the purpose of providing an improved and more efficient drive to the track chain.
Still further, the present invention achieves the aforementioned advantages and objectives and it does so with an assembly which is readily and easily provided and achieved and which can be readily and easily maintained, and even repaired when necessary, and which does not require any special machining such as threading and provision for screws, and it permits readily and easily converting the drive from the center-mounted drive bushing to the conventional track chain bushing drive, and it even permits reversing the center-mounted drive bushing for distributing wear on the bushing.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.